#include <bits/stdc++.h>

using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
int n,g,e[1100],c[1100],dp[5100][1100],ans,ok=1;
int main()
{
    in>>n>>g;
    for(int i=1;i<=n;i++) in>>e[i]>>c[i];
    ans=100000000;
    for(int i=1;i<=g;i++) dp[i][1]=dp[i][0]=100000000;
    for(int i=1;i<=n&&ok;i++)
    {
        for(int j=0;j<g-e[i];j++)
        {
            dp[j+e[i]][i]=min(dp[j+e[i]][i-1],dp[j][i-1]+c[i]);
        }
        for(int j=g-e[i];j<+g;j++)
        {
            ans=min(ans,dp[j][i-1]+c[i]);
        }
        if(ans!=100000000) ok=0;
    }
    if(ans==100000000) out<<-1;
    out<<ans;
    return 0;
}